Local heat transfer characteristics in a single rotating disk and co-rotating disks

Abstract

The present study investigates convective heat/ mass transfer and flow characteristics inside rotating disks. The rotating disks are simulated on the commonly used 3:5 00 hard disk drives (HDD). The experiments are conducted for the various hub heights of 5, 10 and 15 mm in a single rotating disk and 4, 6 and 8 mm in co-rotating disks and for the various rotating Reynolds numbers of 5.53 · 10 4 , 8.53 · 10 4 and 1.13 · 10 5 . To accommodate the general operating conditions of HDD, the experiments are also conducted with an obstruction of rectangular crosssection in the space, which simulates a read-write head arm. A naphthalene sublimation technique is employed to determine the detailed local heat transfer coefficients on the rotating disks using the heat and mass transfer analogy. Flow field measurements are conducted using laser Doppler anemometry (LDA) and numerical calculations are performed simultaneously to analyze the flow patterns induced by disk rotation. The results of a single rotating disk show that the heat transfer on the rotating disk is enhanced considerably according to the reduction of the hub height and the increase of the rotating Reynolds number. The head arm inserted in the cavity between the rotating disk and the cover enhances uniformity of the heat/mass transfer on the disk due to the deficit of the momentum in the average flow despite the enhancement of the tangential component of fluctuation velocity. The heat/mass transfer rates on the co-rotating disks have very low values near the hub in the inner region of the solidbody rotation and increase rapidly toward the outer region. The change of heat/mass transfer for various hub heights is negligible.

Dynamic interaction of heat transfer, air flow and disc vibration of disc drives — Theoretical development and numerical analysis

“…These are not quite true for hard/optical disc drives in an enclosure and with the heat sources of heat flux type, as indicated theoretically and experimentally by Cho et al [13], Ng et al [21], Tan et al [22] and Yang et al [23]. (2) The aerodynamic heating effect due to fluid's viscous dissipation was considered to be small and even neglected in the energy equation of the rotating disc systems [10][11][12][14][15][16][17]19,20], whereas the decrease of disc temperature at its outer edge found in the numerical simulation cannot be confirmed by the experimental observation by Kameya et al [24].…”

“…d/dr Superscript $ conversion matrix or vector at heat flux boundaries Superscript^(I P or J P rows, I P or J P columns) elements in a matrix; (I P or J P rows) elements in a vector Superscript À (I P or J P rows, i B or j B columns) elements in a matrix; (i B or j B rows) elements in a vector Constant normal upright 'A' Matrix bold upright 'A' Variable normal italic 'A' Vector bold italic 'A' Effects of disc contraction and rotation, heat transfer and permeability of the discs on the viscous fluid flow and temperature distributions between heated contracting rotating discs were analysed by Nazir and Mahmood [11] and Si et al [12]. Below the critical rotating Reynolds number in the laminar flow regime, Cho et al [13] investigated the local convective heat/mass transfer and flow characteristics on a single rotating disc and co-rotating discs with a cylindrical shroud. Chen [14] studied effects of disc rotation and buoyancy force on the entropy generation inside disc-driven rotating convectional flow.…”

Design of swing arm type actuators considering thermal and dynamic characteristics

“…In the inkjet printhead by MEMS process, the thermal fatigue stress is analyzed by FEM (Park and Choi 2005). Furthermore, the heat transfer of hard disk drive (HDD) rotating disk is researched by Cho et al (2003). Recently, Lee et al (2006) suggested a micro thermal design of a swing arm type SFF optical pick up system; however, the design is only concerned about the thermal characteristics from heat emission from optical pick up unit without dynamic consideration and the convection coefficient is assumed without verifications.…”

Hall effects on unsteady hydromagnetic flow induced by an eccentric–concentric rotation of a disk and a fluid at infinity

“…In view of its wide applications in industrial and other technological fields, the problem of flow near a rotating disk has been extended to hydromagnetics. One of the major applications of the MHD rotating disk flow is the manufacture of the magnetic hard disk drives (HDD) with high information storage capacity [1]. The hydromagnetic flow due to a rotating disk was first investigated by Katukani [2].…”